Swarm/DysonNetwork.Sphere/ActivityPub/ActivityPubActivityProcessor.cs

using DysonNetwork.Shared.Models;
using Microsoft.EntityFrameworkCore;
using NodaTime;
using System.Text.Json;

namespace DysonNetwork.Sphere.ActivityPub;

public class ActivityPubActivityProcessor(
    AppDatabase db,
    ActivityPubSignatureService signatureService,
    ActivityPubDeliveryService deliveryService,
    ActivityPubDiscoveryService discoveryService,
    ILogger<ActivityPubActivityProcessor> logger
)
{
    public async Task<bool> ProcessIncomingActivityAsync(
        HttpContext context,
        string username,
        Dictionary<string, object> activity
    )
    {
        if (!signatureService.VerifyIncomingRequest(context, out var actorUri))
        {
            logger.LogWarning("Failed to verify signature for incoming activity");
            return false;
        }
        
        if (string.IsNullOrEmpty(actorUri))
            return false;
        
        var activityType = activity.GetValueOrDefault("type")?.ToString();
        logger.LogInformation("Processing activity type: {Type} from actor: {Actor}", activityType, actorUri);
        
        switch (activityType)
        {
            case "Follow":
                return await ProcessFollowAsync(actorUri, activity);
            case "Accept":
                return await ProcessAcceptAsync(actorUri, activity);
            case "Reject":
                return await ProcessRejectAsync(actorUri, activity);
            case "Undo":
                return await ProcessUndoAsync(actorUri, activity);
            case "Create":
                return await ProcessCreateAsync(actorUri, activity);
            case "Like":
                return await ProcessLikeAsync(actorUri, activity);
            case "Announce":
                return await ProcessAnnounceAsync(actorUri, activity);
            case "Delete":
                return await ProcessDeleteAsync(actorUri, activity);
            case "Update":
                return await ProcessUpdateAsync(actorUri, activity);
            default:
                logger.LogWarning("Unsupported activity type: {Type}", activityType);
                return false;
        }
    }

    private async Task<bool> ProcessFollowAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var actor = await GetOrCreateActorAsync(actorUri);
        var targetPublisher = await db.Publishers
            .FirstOrDefaultAsync(p => p.Name == ExtractUsernameFromUri(objectUri));
        
        if (targetPublisher == null)
        {
            logger.LogWarning("Target publisher not found: {Uri}", objectUri);
            return false;
        }
        
        var existingRelationship = await db.FediverseRelationships
            .FirstOrDefaultAsync(r => 
                r.ActorId == actor.Id && 
                r.TargetActorId == actor.Id && 
                r.IsLocalActor);
        
        if (existingRelationship != null && existingRelationship.State == RelationshipState.Accepted)
        {
            logger.LogInformation("Follow relationship already exists");
            return true;
        }
        
        if (existingRelationship == null)
        {
            existingRelationship = new SnFediverseRelationship
            {
                ActorId = actor.Id,
                TargetActorId = actor.Id,
                IsLocalActor = true,
                LocalPublisherId = targetPublisher.Id,
                State = RelationshipState.Pending,
                IsFollowing = false,
                IsFollowedBy = true
            };
            db.FediverseRelationships.Add(existingRelationship);
        }
        
        await db.SaveChangesAsync();
        
        await deliveryService.SendAcceptActivityAsync(
            targetPublisher.Id,
            actorUri,
            activity.GetValueOrDefault("id")?.ToString() ?? ""
        );
        
        logger.LogInformation("Processed follow from {Actor} to {Target}", actorUri, objectUri);
        return true;
    }

    private async Task<bool> ProcessAcceptAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var actor = await GetOrCreateActorAsync(actorUri);
        
        var relationship = await db.FediverseRelationships
            .Include(r => r.Actor)
            .Include(r => r.TargetActor)
            .FirstOrDefaultAsync(r => 
                r.IsLocalActor && 
                r.TargetActorId == actor.Id && 
                r.State == RelationshipState.Pending);
        
        if (relationship == null)
        {
            logger.LogWarning("No pending relationship found for accept");
            return false;
        }
        
        relationship.State = RelationshipState.Accepted;
        relationship.IsFollowing = true;
        relationship.FollowedAt = SystemClock.Instance.GetCurrentInstant();
        
        await db.SaveChangesAsync();
        
        logger.LogInformation("Processed accept from {Actor}", actorUri);
        return true;
    }

    private async Task<bool> ProcessRejectAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var actor = await GetOrCreateActorAsync(actorUri);
        
        var relationship = await db.FediverseRelationships
            .FirstOrDefaultAsync(r => 
                r.IsLocalActor && 
                r.TargetActorId == actor.Id);
        
        if (relationship == null)
        {
            logger.LogWarning("No relationship found for reject");
            return false;
        }
        
        relationship.State = RelationshipState.Rejected;
        relationship.IsFollowing = false;
        relationship.RejectReason = "Remote rejected follow";
        
        await db.SaveChangesAsync();
        
        logger.LogInformation("Processed reject from {Actor}", actorUri);
        return true;
    }

    private async Task<bool> ProcessUndoAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectValue = activity.GetValueOrDefault("object");
        if (objectValue == null)
            return false;
        
        var objectDict = objectValue as Dictionary<string, object>;
        if (objectDict != null)
        {
            var objectType = objectDict.GetValueOrDefault("type")?.ToString();
            switch (objectType)
            {
                case "Follow":
                    return await UndoFollowAsync(actorUri, objectDict.GetValueOrDefault("id")?.ToString());
                case "Like":
                    return await UndoLikeAsync(actorUri, objectDict.GetValueOrDefault("id")?.ToString());
                case "Announce":
                    return await UndoAnnounceAsync(actorUri, objectDict.GetValueOrDefault("id")?.ToString());
                default:
                    return false;
            }
        }
        
        return false;
    }

    private async Task<bool> ProcessCreateAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectValue = activity.GetValueOrDefault("object");
        if (objectValue == null || !(objectValue is Dictionary<string, object> objectDict))
            return false;
        
        var objectType = objectDict.GetValueOrDefault("type")?.ToString();
        if (objectType != "Note" && objectType != "Article")
        {
            logger.LogInformation("Skipping non-note content type: {Type}", objectType);
            return true;
        }
        
        var actor = await GetOrCreateActorAsync(actorUri);
        var instance = await GetOrCreateInstanceAsync(actorUri);
        
        var contentUri = objectDict.GetValueOrDefault("id")?.ToString();
        if (string.IsNullOrEmpty(contentUri))
            return false;
        
        var existingContent = await db.FediverseContents
            .FirstOrDefaultAsync(c => c.Uri == contentUri);
        
        if (existingContent != null)
        {
            logger.LogInformation("Content already exists: {Uri}", contentUri);
            return true;
        }
        
        var content = new SnFediverseContent
        {
            Uri = contentUri,
            Type = objectType == "Article" ? FediverseContentType.Article : FediverseContentType.Note,
            Title = objectDict.GetValueOrDefault("name")?.ToString(),
            Summary = objectDict.GetValueOrDefault("summary")?.ToString(),
            Content = objectDict.GetValueOrDefault("content")?.ToString(),
            ContentHtml = objectDict.GetValueOrDefault("contentMap")?.ToString(),
            PublishedAt = ParseInstant(objectDict.GetValueOrDefault("published")),
            EditedAt = ParseInstant(objectDict.GetValueOrDefault("updated")),
            IsSensitive = bool.TryParse(objectDict.GetValueOrDefault("sensitive")?.ToString(), out var sensitive) && sensitive,
            ActorId = actor.Id,
            InstanceId = instance.Id,
            Attachments = ParseAttachments(objectDict.GetValueOrDefault("attachment")),
            Mentions = ParseMentions(objectDict.GetValueOrDefault("tag")),
            Tags = ParseTags(objectDict.GetValueOrDefault("tag")),
            InReplyTo = objectDict.GetValueOrDefault("inReplyTo")?.ToString()
        };
        
        db.FediverseContents.Add(content);
        await db.SaveChangesAsync();
        
        logger.LogInformation("Created federated content: {Uri}", contentUri);
        return true;
    }

    private async Task<bool> ProcessLikeAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var actor = await GetOrCreateActorAsync(actorUri);
        var content = await db.FediverseContents
            .FirstOrDefaultAsync(c => c.Uri == objectUri);
        
        if (content == null)
        {
            logger.LogWarning("Content not found for like: {Uri}", objectUri);
            return false;
        }
        
        var existingReaction = await db.FediverseReactions
            .FirstOrDefaultAsync(r => 
                r.ActorId == actor.Id && 
                r.ContentId == content.Id &&
                r.Type == FediverseReactionType.Like);
        
        if (existingReaction != null)
        {
            logger.LogInformation("Like already exists");
            return true;
        }
        
        var reaction = new SnFediverseReaction
        {
            Uri = activity.GetValueOrDefault("id")?.ToString() ?? Guid.NewGuid().ToString(),
            Type = FediverseReactionType.Like,
            IsLocal = false,
            ContentId = content.Id,
            ActorId = actor.Id
        };
        
        db.FediverseReactions.Add(reaction);
        content.LikeCount++;
        
        await db.SaveChangesAsync();
        
        logger.LogInformation("Processed like from {Actor}", actorUri);
        return true;
    }

    private async Task<bool> ProcessAnnounceAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var actor = await GetOrCreateActorAsync(actorUri);
        var content = await db.FediverseContents
            .FirstOrDefaultAsync(c => c.Uri == objectUri);
        
        if (content != null)
        {
            content.BoostCount++;
            await db.SaveChangesAsync();
        }
        
        logger.LogInformation("Processed announce from {Actor}", actorUri);
        return true;
    }

    private async Task<bool> ProcessDeleteAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var content = await db.FediverseContents
            .FirstOrDefaultAsync(c => c.Uri == objectUri);
        
        if (content != null)
        {
            content.DeletedAt = SystemClock.Instance.GetCurrentInstant();
            await db.SaveChangesAsync();
            logger.LogInformation("Deleted federated content: {Uri}", objectUri);
        }
        
        return true;
    }

    private async Task<bool> ProcessUpdateAsync(string actorUri, Dictionary<string, object> activity)
    {
        var objectUri = activity.GetValueOrDefault("object")?.ToString();
        if (string.IsNullOrEmpty(objectUri))
            return false;
        
        var content = await db.FediverseContents
            .FirstOrDefaultAsync(c => c.Uri == objectUri);
        
        if (content != null)
        {
            content.EditedAt = SystemClock.Instance.GetCurrentInstant();
            content.UpdatedAt = SystemClock.Instance.GetCurrentInstant();
            await db.SaveChangesAsync();
            logger.LogInformation("Updated federated content: {Uri}", objectUri);
        }
        
        return true;
    }

    private async Task<bool> UndoFollowAsync(string actorUri, string? activityId)
    {
        var actor = await GetOrCreateActorAsync(actorUri);
        
        var relationship = await db.FediverseRelationships
            .FirstOrDefaultAsync(r => 
                r.ActorId == actor.Id || 
                r.TargetActorId == actor.Id);
        
        if (relationship != null)
        {
            relationship.IsFollowing = false;
            relationship.IsFollowedBy = false;
            await db.SaveChangesAsync();
            logger.LogInformation("Undid follow relationship");
        }
        
        return true;
    }

    private async Task<bool> UndoLikeAsync(string actorUri, string? activityId)
    {
        var actor = await GetOrCreateActorAsync(actorUri);
        
        var reactions = await db.FediverseReactions
            .Where(r => r.ActorId == actor.Id && r.Type == FediverseReactionType.Like)
            .ToListAsync();
        
        foreach (var reaction in reactions)
        {
            var content = await db.FediverseContents.FindAsync(reaction.ContentId);
            if (content != null)
            {
                content.LikeCount--;
            }
            db.FediverseReactions.Remove(reaction);
        }
        
        await db.SaveChangesAsync();
        return true;
    }

    private async Task<bool> UndoAnnounceAsync(string actorUri, string? activityId)
    {
        var content = await db.FediverseContents
            .FirstOrDefaultAsync(c => c.Uri == activityId);
        
        if (content != null)
        {
            content.BoostCount = Math.Max(0, content.BoostCount - 1);
            await db.SaveChangesAsync();
        }
        
        return true;
    }

    private async Task<SnFediverseActor> GetOrCreateActorAsync(string actorUri)
    {
        var actor = await db.FediverseActors
            .FirstOrDefaultAsync(a => a.Uri == actorUri);
        
        if (actor == null)
        {
            var instance = await GetOrCreateInstanceAsync(actorUri);
            actor = new SnFediverseActor
            {
                Uri = actorUri,
                Username = ExtractUsernameFromUri(actorUri),
                DisplayName = ExtractUsernameFromUri(actorUri),
                InstanceId = instance.Id
            };
            db.FediverseActors.Add(actor);
            await db.SaveChangesAsync();
        }
        
        return actor;
    }

    private async Task<SnFediverseInstance> GetOrCreateInstanceAsync(string actorUri)
    {
        var domain = ExtractDomainFromUri(actorUri);
        var instance = await db.FediverseInstances
            .FirstOrDefaultAsync(i => i.Domain == domain);
        
        if (instance == null)
        {
            instance = new SnFediverseInstance
            {
                Domain = domain,
                Name = domain
            };
            db.FediverseInstances.Add(instance);
            await db.SaveChangesAsync();
            await discoveryService.FetchInstanceMetadataAsync(instance);
        }
        
        return instance;
    }

    private string ExtractUsernameFromUri(string uri)
    {
        return uri.Split('/').Last();
    }

    private string ExtractDomainFromUri(string uri)
    {
        var uriObj = new Uri(uri);
        return uriObj.Host;
    }

    private Instant? ParseInstant(object? value)
    {
        if (value == null)
            return null;
        
        if (value is Instant instant)
            return instant;
        
        if (DateTimeOffset.TryParse(value.ToString(), out var dateTimeOffset))
            return Instant.FromDateTimeOffset(dateTimeOffset);
        
        return null;
    }

    private List<ContentAttachment>? ParseAttachments(object? value)
    {
        if (value == null)
            return null;
        
        if (value is JsonElement element && element.ValueKind == JsonValueKind.Array)
        {
            return element.EnumerateArray()
                .Select(attachment => new ContentAttachment
                {
                    Url = attachment.GetProperty("url").GetString(),
                    MediaType = attachment.GetProperty("mediaType").GetString(),
                    Name = attachment.GetProperty("name").GetString()
                })
                .ToList();
        }
        
        return null;
    }

    private List<ContentMention>? ParseMentions(object? value)
    {
        if (value == null)
            return null;
        
        if (value is JsonElement element && element.ValueKind == JsonValueKind.Array)
        {
            return element.EnumerateArray()
                .Where(e => e.GetProperty("type").GetString() == "Mention")
                .Select(mention => new ContentMention
                {
                    Username = mention.GetProperty("name").GetString(),
                    ActorUri = mention.GetProperty("href").GetString()
                })
                .ToList();
        }
        
        return null;
    }

    private List<ContentTag>? ParseTags(object? value)
    {
        if (value == null)
            return null;
        
        if (value is JsonElement element && element.ValueKind == JsonValueKind.Array)
        {
            return element.EnumerateArray()
                .Where(e => e.GetProperty("type").GetString() == "Hashtag")
                .Select(tag => new ContentTag
                {
                    Name = tag.GetProperty("name").GetString(),
                    Url = tag.GetProperty("href").GetString()
                })
                .ToList();
        }
        
        return null;
    }
}